Safety fence for roads



March 7,1967 MULLER ET AL SAFETY FENCE FOR ROADS 4 Sheets-Sheet 1 Filed July 25, 1964 INVNTOR5 H M01452 q- H. BE/erR/w ZZ QL MM ATTY March 7, 1967 Filed July 25 1964 FIGJZ a I f: 23 23 H. MULLER T AL SAFETY, FENCE FOR ROADS 4 Sheets-Sheet 2 FIG.3

lNVENTOIRF H MULLER 9 H BEKTRAM ATT Y5.

March 7, 1967 U L ET AL SAFETY FENCE FOR ROADS Filed July 25 19 4 4 Sheets-Sheet 5 FIGAI INVENTORS H N01 LEE A. BEETZA/W ATTY- March 7,1967 MULLE Em 3,307,833

SAFETY FENCE FOR ROADS Filed July 25 1964 4 Sheets-Sheet 4 FIG. 6

4/ I 42 4a 44 O O m-h 0 (L Y H MULLER?! H. BERT/2A United States Patent 4 Claims. 61. 256--13.1)

This invention relates to safety fences for roads. Many serious accidents on roads, especially highways or speedways, are caused 'by motor vehicles unintentionally changing their direction of travel and thus either getting on the opposite lane or off the road.

To prevent motor vehicles from getting off the road, sectional steel guide rails have hitherto been used. In the course of time, however, it has proved that such guide rails do not in every case afford protection because they run over and demolished by heavy vehicles. Even smaller motor vehicles running at high speed against the guide rails have been known to break therethrough I or tumble thereover.

Other known safety devices for roads are the so-called guide posts which are provided with predetermined breaking zone some distance above the ground. These guide posts are not capable, either, of preventing accidents, for when a vehicle collides with a post this is sheared off and a gap results through which the vehicle can get onto the opposite lane and cause serious accidents.

Moreover, so -called fences are known in which posts are mounted in sockets fitted in foundations and horizontally extending cables are secured to the posts at various levels thereof. Safety fences of this kind, in which the posts used are not provided with predetermined breaking zones, have already been tested in the United States.

It is the object of the present invention to improve and develop the last-mentioned safety fences.

To attain this object, the invention provides a safety fence for bounding at least one side of a road and which comprises a plurality of ground-embedded foundations arranged in spaced vertical relationship at the side of the road, a socket fitted in each of said foundations, a cast-iron shearing pin having a lower and an upper end portion and a collar as well as a portion of reduced diameter between the end portions, said lower end portion being inserted in the socket, a post having a lower end portion engaging over the upper end portion of the shearing pin, and a plurality of horizontally extending cables attached to the post at different levels thereof to ensure that in a collision of a motor vehicle with said safety fence said motor vehicle is not permitted to run over or slip through said safety fence, said portion of reduced diameter constituting a predetermined breaking zone, the strength and the elongation at fracture of the material of said shearing pin and the cross section thereof being such as to ensure that in response to an impact caused by said motor vehicle the shearing pin of a consecutive number of posts well shear off thereby to permit said cables to get slackened to a certain extend and thus to gradually destroy the transverse force of, and simultaneously brake and reorient, said motor vehicle sliding along said slackened cables.

Further objects of the invention will become apparent from the following detail description.

An embodiment of the invention will now be described 3,307,833 Patented Mar. 7, 1967 by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is an elevational view, partly in section, of a safety fence according to the invention;

FIG. 2 is an end view of the safety fence;

FIG. 3 is a vertical section, on an enlarged scale, through a post of the safety fence and a socket fixed in a ground-embedded foundation, the post and the socket being interconnected by means of a shearing pin;

FIG. 4 is an elevational view, on a further enlarged scale, of the shearing pin.

FIG. 5 is a top planview of a clamping device arranged to locate a pair of cables on a post shown in cross section, and

FIG. 6 is a schematic view showing the safety fence in four consecutive phases from the moment it is run against Iby a motor vehicle to the moment the motor vehicle has been reoriented and brought to a standstill by the safety fence.

FIGS. 1 and 2 show a safety fence according to the invention, which comprises a plurality of posts of which only one post 20 is illustrate-d as mounted in a socket 21 by means of a shearing pin 22. The socket 21 is fixed in a ground-embedded foundation 3a.

As will be seen especially from FIG. 2, pairs of parallel cables 3, 4, 5 and 6 are secured to the post 20 at different levels thereof by means of clamping devices to be described hereinafter. The individual cables of each pair of cables 3, 4, 5 and 6 extend on opposite sides of the post 20 and thus are spaced from each other by the diameter of the post 20. The cables are tensioned by means of tensioning devices 7 (FIG. 1). On either side of the post 20, wire nettings 23 are attached to the respective cables 3, 4, 5 and 6.

The lower pair of cables 3, 4 and 5 are conveniently chosen of a diameter of 14 mm., whereas the upper pair of cables 6 should have a larger diameter, eg of 19 mm. or more. Expediently, the upper pair of cables 6 is arranged about 1 meter above road level. 4

Referring to FIGS. 3 and 4, the shearing pin 22 interconnecting the post 20 and the socket 21 has a lower end portion 26 inserted in the socket 21, an upper end portion 25 inserted in the post 20 and a collar 27 intermediate its upper and lower end portions 25 and 26, respectively. The collar 27 has a diameter larger than the respective diameters of the upper end portion 25 and the lower end portion 26 of the shearing pin 22 and forms a lower annular end face 28 abutting against the socket 21, and an upper annular end face 29 supporting the post 20. This arrangement establishes a simply manageable connection. As can be seen particularly from FIG. 4, the upper end portion 25 has a portion 30 of reduced diameter at its end adjoining the upper end face 29 of the collar 27, which portion 30 constitutes a predetermined breaking zone. In the present case, the diameter of the reduced portion 30 is about 60 mm., which has proved convenient in a series of tests. In some cases even a larger shearing cross section may be used.

The shearing pin 22 is cast in one piece and provided with recesses 31 to save material.

A particular advantage of the shearing pin 22 is that it can be replaced in a simple manner. The collar 27 formes a satisfactory transition from the socket 21 to the post 20 in that there are no projecting parts that might constitute a danger in an accident. Due to the fact that the socket 21 is closed by the lower annular end face 28 of the collar 27, water is prevented from entering the socket 21.

A further important feature of the proposed safety fence is constituted by the fact that when a motor vehicle runs against the safety fence this will yield to the impact upon breakage of the shearing pins 22, maintaining, however, in any event its vertical position so that it cannot be run over. Therefore, the safety fence must have an appropriate height, e.g. of 1 meter, and the pairs of cables 3, 4, 5 and 6 are appropriately distributed over this height.

Referring to FIG. 5, the mentioned clamping device used for securing, in the illustrated embodiment, the pair of cables 6 to the post 20 consists of two stirrup clamps 32 and 33 interlocked by threaded joints 34. By this clamping device, the cables 6 are located on opposite sides of the post 20 but nevertheless permitted of longitudinal displacement to yield to the impact caused by a motor vehicle running against the safety fence. The threaded joints 34 are disposed in the free space between the pair of cables 6 so that externally the safety fence is free from pointed or projecting parts. The same also applies to the pairs of cables 3, 4 and 5 which are secured to the post 20 by similar clamping devices.

As to the material used for the shearing pins 22, satisfactory results have been obtained with G6 26 (corresponding to AISI Class 40 Medium Section) which, according to International Standards, is a gray cast iron containing lamellary graphite and having a minimum tensile strength of 16.506 t./sq. in.

FIG. 6 schematically illustrates in four different phases 41, 42, 43 and 44 the mode of operation of the safety fence. In the first phase 41, a motor vehicle M is shown to run at an angle 1x1 against the safety fence between two posts I and II thereof. The cables yield and attenuate the impact. The impact causes the shearing pins of the posts I and II to shear off, whereby part of the transverse force of the motor vehicle M is destroyed. At the same time, the cables further yield as they get slackened over a long distance upon the breakage of the shearing pins and thus of the posts I and II. While sliding along the slackened cables, the motor vehicle M is slightly reoriented, as can be seen from the decreased angle (X2 in phase 42.

In phase 42, the motor vehicle M successively breaks the shearing pins of two further posts III and IV, whereby again part of the transverse force is destroyed while the slackened length of the cables and thus their yieldingness is increased. 'By sliding further along the slackened cables, the motor vehicle M again is slightly reoriented. In phase 43, finally, the shearing pin of another post, designated by V, is ruptured, whereby the remaining transverse force is destroyed. The longitudinal axis of the motor vehicle M now extends nearly parallel to the safety fence, that is to say, it has substantially been reoriented to its original direction of travel. Simultaneously, the motor vehicle M has been brought to a standstill owing to the friction produced by sliding along the cables of the safety fence.

This sequence will be obtained only if the predetermined Tbreaking zone formed by the reduced portion 30 (FIG. 4) of the upper portion of the shearing pin is properly di- Inensioned. In this conjunction, the shearing pin matetrial is of importance in addition to the shearing cross section or the section modulus. What matters in the first place is the resistance to rupture and the breaking elongation of the shearing pin material. Based on this knowledge, the invention proposes cast iron as a shearing pin material because with cast iron these factors can be determined with sufiicient accuracy and will not change, either, in the course of time, for example by atmospheric influences. It is self-evident that the number of posts of which the shearing pins are sheared off may be larger or smaller than shown in FIG. 6, which depends on the speed and weight of the motor vehicle M and on the angle with which it runs against the safety fence.

As is further illustrated by FIG. 6, the motor vehicle M while sliding along the progressively slackening cables is gradua y reo ented 0 its original direction of travel.

By the frictional engagement with the cables, mainly the longitudinal force of the motor vehicle M is destroyed. The braking efiiciency of the safety fence is increased by the wire nettings 23 (FIGS. 1 and 2) attached to the cables of the safety fence. When the motor vehicle M brushes along over the safety fence, these wire nettings are pushed together and thus produce a cushioning effect.

The material of the shearing pins must be such as to ensure that over a given distance L of the safety fence all shearing pins will be sheared off. Consequently, the material must have a certain brittleness. Experiments carried out with gray cast iron GG 26 (corresponding to AISI Class 40 Medium Section) have been successful.

On the other hand, attention is to be paid to the fact that the impact may cause successive explosion-like breakage of the immediately concerned posts, or rather, of the shearing pins thereof, which again will cause the cables to vibrate. It has to be avoided that such vibration of the cables results in the rupture also of such shearing pins as pertain to posts not directly engaged in the interception of the motor vehicle that has collided with the safety fence. This requirement puts a limit to the brittleness of the shearing pins. In view of this, also pearlite iron with a nickel addition and an increased elongation at fracture of 3% has been successfully used as a shearing pin material.

The data stated impart to one skilled in the art a teaching sufiiciently exact to permit the realization of a safety fence as proposed by the present invention. In each specific case, the values will be chosen so as to be within or to pass the indicated limits. It will likewise be necessary to dimension the shearing pins in agreement with the post spacing. A post spacing of 2.50 meters has had satisfactory results.

In phase 44 of FIG. 6, h designates a further value to be taken into consideration. Precisely, the value h gives the measure by which the safety fence has yielded to the impact of the motor vehicle M during the collision and must not exceed, for example, three meters least the intercepted motor vehicle M all the same endanger, or collide with, the opposing traffic. The slackened cables are deflected from normal by an angle A. l

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

We claim:

1. In a safety fence for delineating at least one boundary of a road and to prevent a colliding automobile from escaping that boundary, the combination comprising a plurality of spaced post members, each of said post members having a socket member, said socket member being firmly embedded and protruding from the ground along the edge of the road; a shearing pin for each of the socket members, said shearing pin having an upper and a lower portion, said lower portion being accepted within the protruding portion of said socket member, said shearing pin having a weakened portion thereon which will fail upon the introduction of a predetermined force; a post member detachably attached to said shearing pin and vertically spaced, along said shearing pin, from said socket member, said upper portion of said shearing pin being accepted within said post member, said shearing pin having a collar portion, said collar portion having a diameter larger than said upper and lower portions, said collar portion overlying the protruding end of said socket member and separating said socket member and said post member; and, yieldable cable means fixedly attached to each of said post members thereby interconnecting said post members, said cable means constraining the impact force of and reorienting the direction of a colliding vehicle through the increase of slack caused by yielding of the cable means which results when a colliding vehicle creates a sufiicient force on the cable means to cause the shearing pins to fail and the post members and socket members joined thereby to become disoriented.

2. In a safety fence as defined in claim 1 wherein said upper portion of said shearing pin has a weakened section thereon which will fail upon the introduction of a predetermined force to separate said post member from said socket member thereby creating the necessary slack in said cable to retard and reorient the colliding vehicle.

3. In a safety fence as defined in claim 1 wherein said yieldable cable means comprises a pair of horizontally separated cables spaced apart from each other by the diameter of the post member.

4. In a safety fence as defined in claim 3 wherein said combination further comprises a wire netting fixedly attached to said spaced cables to further absorb and reorient the force of the colliding vehicle.

References Cited by the Examiner UNITED STATES PATENTS Cunningham et al.

Brown 25655 Prater 52296 Solomon 52-296 Beckwith 52296 X MacDonald 256--13.1 Gleason et a1. 25613.1

Edge 25613.1 'Bhend 52-292 Galamba 25659 X Mueller et al.

Bieber.

Switzerland.

HARRISON R. MOSELEY, Primary Examiner. 20 D. L. TAYLOR, Assistant Examiner. 

1. IN A SAFETY FENCE FOR DELINEATING AT LEAST ONE BOUNDARY OF A ROAD AND TO PREVENT A COLLIDING AUTOMOBILE FROM ESCAPING THAT BOUNDARY, THE COMBINATION COMPRISING A PLURALITY OF SPACED POST MEMBERS, EACH OF SAID POST MEMBERS HAVING A SOCKET MEMBER, SAID SOCKET MEMBER BEING FIRMLY EMBEDDED AND PROTRUDING FROM THE GROUND ALONG THE EDGE OF THE ROAD; A SHEARING PIN FOR EACH OF THE SOCKET MEMBERS, SAID SHEARING PIN HAVING AN UPPER AND A LOWER PORTION, SAID LOWER PORTION BEING ACCEPTED WITHIN THE PROTRUDING PORTION OF SAID SOCKET MEMBER, SAID SHEARING PIN HAVING A WEAKENED PORTION THEREON WHICH WILL FAIL UPON THE INTRODUCTION OF A PREDETERMINED FORCE; A POST MEMBER DETACHABLY ATTACHED TO SAID SHEARING PIN AND VERTICALLY SPACED, ALONG SAID SHEARING PIN, FROM SAID SOCKET MEMBER, SAID UPPER PORTION OF SAID SHEARING PIN BEING ACCEPTED WITHIN SAID POST MEMBER, SAID SHEARING PIN HAVING A COLLAR PORTION, SAID COLLAR PORTION HAVING A DIAMETER LARGER THAN SAID UPPER AND LOWER PORTIONS, SAID COLLAR PORTION OVERLYING THE PROTRUDING END OF SAID SOCKET MEMBER AND SEPARATING SAID SOCKET MEMBER AND SAID POST MEMBER; AND YIELDABLE CABLE MEANS FIXEDLY ATTACHED TO EACH OF SAID POST MEMBERS THEREBY INTERCONNECTING SAID POST MEMBERS, SAID CABLE MEANS CONSTRAINING THE IMPACT FORCE OF AND REORIENTING THE DIRECTION OF A COLLIDING VEHICLE THROUGH THE INCREASE OF SLACK CAUSED BY YIELDING OF THE CABLE MEANS WHICH RESULTS WHEN A COLLIDING VEHICLE CREATES A SUFFICIENT FORCE ON THE CABLE MEANS TO CAUSE THE SHEARING PINS TO FAIL AND THE POST MEMBERS AND SOCKET MEMBERS JOINED THEREBY TO BECOME DISORIENTED. 